Switch



Aug5 1941- P. s. BEAR 2,251,315

' SWITCH Filed March 2, 1938 3 Sheets-Sheet 1 Aug 5, 1941. p. SjBEAR#'2,251,315'

swIvTcH Filed March 2, 1958 5 Sheets-Sheet 2 if yfmfwww P. S. BEAR Aug5, 1941.

5 sheets-smet s SWITCH Filed March 2, 1958 INVENTOR. P/V 6- BERE#22M/775.' MMM A TTORN E YS.

Patented Aug. 5, i941 SWITCH Paul S. Bear, Elkhart, Ind., assigner, bymesne assignments, to Bucklen-Bear Laboratories, Inc., Elkhart, Ind., acorporation of Indiana Application March Z, 1938, Serial No. 193,464

(Cl. 20G-152) l Claims.

This invention relates to switches, and more particularly is directed toa switch of the metallic envelope type using a liquid contactorformaking and breaking the circuit through the switch.

The present application is directed generally to switch structures ofthe type shown in my copending application, Serial No. 745,842, filedSeptember 28, 1934, of which this application is a c-ontinuation inpart, with certain modifications and improvements in the structure oithe switch and certain improvements in the manner of enclosing theswitch for use in various situations.

It is one of the primary objects of my invention to provide a switchstructure of the type having a metal envelope or shell closed at oneend, and arranged at the opposite end to receive a ceramic insert whichin turn supports an electrode within the open end of the envelope. Theopen end of the shell is spun over to secure the insert and electrode inxed position within the switch envelope and to provide an effectiveseal. Suitable gasket means are provided between the insert and theenvelope and between the electrode and the insert for preventing anyleakage therethrough. In the preferred embodiment of the presentinvention, such gasket means are of a type capable ci withstandingrelatively high pressures and temperatures which may be employed insituations Where the switch envelope is subjected to high temperatures,or where relaf tively high internal pressures may develop.

Another feature of the present invention is the provision of a noveltype of terminal lug construction for facilitating the connection ofterminal conductors to the terminal points of the switch structure. Thistype of terminal construction is especially desirable when the switchenvelope is to be enclosed within a case member such as a molded case orthe like as described in detail in my copending application Serial No.53,146, filed December 6, 1935, now Patent No. 2,132,921, issued October11, i938.

Another feature of the present invention is the provision of a switchstructure provided with suitable gaskets which means and have thecharacteristic of withstanding high temperatures caused by the coatingof the switch with rubber or the like.

I have found that one of the restrictions against use of glass some ofthe earlier forms of the metal envelope switches, has been the inabilityto immerse the same in hot solutions, acids, alkalies, vapors or thelike. With the construction disclosed herein, I `am able to provide amercury switch which are effective as sealing type mercury switches, or

can be directly immersed in hot acid solutions, alkaline solutions, orany other deteriorating solutions, without in any way affecting theswitch envelope, switch parts or operating. mechanisms. This isaccomplished by coating the entire switch envelope and leads with arelatively heavy coating of material such as Neoprene or a similarchemical and temperature resisting material.

The switch if coated in this manner is entirely covered, together withits leads, by a coating of sufficient thickness to prevent any possiblecontact of the switch parts with the solution in which it may beimmersed. However, in order to apply such a coating to the switch,relatively high temperatures are necessary for vulcanizing, and it istherefore essential that the gasket means in the switch be of aconstruction such that they will withstand these temperatures withoutany loss of sealing ability or resiliency.

For this reason I preferably employ a metallic asbestos gasket, orgaskets, comprising a copper, stainless steel, or aluminum sheetenclosing the asbestos, which are readily deformable under pressure intosealing engagement between Vthe respective parts, and are able towithstand relatively high temperatures 4and pressures without any lossof effectiveness as a sealing means.

It is also an object of the present invention to provide a doublecircuit switchcontrol mechani'sm, which embodies two metal envelopeswitches of the type employed herein, soldered, or otherwise secured inend to end relation so that tilting of the switch in either directioncauses opening of one circuit and closing of a second circuit. With sucha construction I have provided also a novel type of molded enclosingcase which is formed to fit closely about the switch parts, and providesa full. protection for the switch against corrosive atmosphericconditions or the like, and also enhances, to an appreciable extent, theappearance of the switch itself. With such a construction, I preferablyincorporate our novel terminal lug assembly to facilitate the connectionand disconnection of conductors to the terminals of the switch.

Other objects and advantages of the present invention will appear morefully from the following detailed description, which taken inconjunction with the accompanying drawings, will disclose to thoseskilled in the art the particular construction and operation of apreferred form of the present invention.

In the drawings:

Figure 1 is an elevational view, partly in secy tion, of a switchenvelope constructed in accordance with the present invention;

Figure 2 is an enlarged elevational view of one end of the completedswitch;

Figure 3 is an end elevational View of the portion of the switch shownin Figure 2;

Figure 4 shows a modied manner of attaching 'a terminal co-nductor to aswitch terminal;

Figure 5 shows the completed connection of Figure 4;

Figure 6 is an eleva'tional view of a switch covered with a protectivecoating, the switch per se being shown in dotted lines;

Figure 7 shows the switch of Figure 6 in plan;

Figure 8 is an enlarged view of one of the members used to form a moldedcasing for a double acting switch structure;

Figure 9 is an end elevational view of the member shown in Figure 8;

Figure 10 is an elevational View of a double acting switch structure;

Figure 1'1 is an elevational view of the switch structure shown inFigure 10 provided with the molded cover of Figures 8 and 9;

Figure 12 is `a sectional View thorugh a modified form of switchemploying the gasket means of the switch shown in Figure 1;

VFigure 13 is a transverse sectional view through a switch operating inthe 'manner of the switch shown in Figure 1'2;

Figure 14 is a sectional view through the switch shown in Figure 13; and

Figure 15 is a View showing the switch in Figure 13 in switch closedposition.

VReferring now in detail to the drawings, I l

have shown in Figure 1 a metallic switch envelope 5 which is preferablya drawn metal shell having the closed end 6 and an enlarged cylindricalend 'I joined to the main body portion by the frusto-conical shoulder 8.the enlarged open end 'I of theswitch is a ceramic insert 9 having thetapered bore I0 opening toward the elongated body portion of the shell5.

At its smaller end the bore IIJ terminates in a radially extendingshoulder I2 which forms an acute angled cutting edge of the typedescribed in detail in my lcopending application, Serial No. 53,146,filed December 6, 1935. .At the outer periphery of the shoulder I2 anaxially extending cylindrical wall I3 is provided which terminates in aradially outwardly extending shoulder I4 separated from the externalsurface of the insert by the cylindrical flange I5.

Disposed between the external tapered surface of the insert 9 and theinternal surface of the frusto-conical shoulder 8 I provide a gasketmember I6 of frusto--conical form, this gasket member consisting of ametallic annulus I'I which encloses an asbestos annulus I8. Axialpressure on the insert 9 is adapted to compress *the metallic asbestosgasket I6 into sealing en gagement between the insert and the shoulder 8to provide a seal for effectively preventing loss of pressuretherebetween.

Seated in the annular opening defined by the sur-face I3 is an electrode2U having a peripheral Vshoulder 22 seated against a similar metallicasbestos gasket 23 which bears against `the shoul- Axial pressure on theder I4 ofV the insert. Velectrode therefore results in compression ofthe gasket 23 to provide an effective seal between the interior of theinsent 9 and the electrode 2li. The front or inner radial face of theelectrode 20 forms with the shoulder I2 an annular groove Disposedwithin f which is adapted to retain a body of mercury 24 in stableposition therein. This retention of the stable body of mercury is forthe purpose of insuring positive repeat performance of the switch; thatis to say, the switch will open and close the circuit at the sameoperating angles due to the retained body of mercury 24 being of suchvolume as to retain its stability and position regardless of theinclination of the switch within the operating range. A second body ofmercury 25 is disposed within the body portion of the shell 5 and isadapted to move up and down the surface of the bore I8 into and out ofcontact with the stable body of mercury 24 to make and break the-circuit lthrough the switch.

The electrode 20 has an outwardly extending shank portion 26 whichserves as one terminal of the switch, and which is adapted to projectthrough a ceramic spacing member 2'I preferably formed of a thermallyrefractive member, such as described in detail in the copendingapplication of Herbert E. Bucklen and myself Serial No, 148,946, filedJune 18, 1937. A compression washer 28 preferably of metal, engagesabout the shoulder formed on the spacing mem# ber 21, and in theassembly of the switch structure is suitably engaged by pressure headfor moving the entire insert and electrode assembly axially into theenvelope 5 to compress the gaskets I6 and 23, and to hold the same inpositive sealed position while suitable spinning rolls engage 'the outerend of the enlarged portion 'I of the shell and spin the same over asindicated at 29 to thereby hold the assembly in sealed position. Withsuch a construction, the assembly is :capable of withstanding internalpressures in excess of 4,000 pounds per square inch with no leakage ordestruction of the parts.

.After the insert and electrode have been sealed in position in theenlarged end of the switch, the mercury is introduced through the tappedopening 32 in the small end of the switch, andl the internal volume ofthe switch is then evacuated thoroughly and the switch is sealed bymeans of the sealing plug 33. If desired, a liquid ll of the typedisclosed in detail in my cepending appli-cation, Serial No. 745,842,filed September 28, 1934, may be introduced into the interior of theenvelope for the purpose of increasing the meniscus height of themercury and for increasing the heat dissipatng characteristics andstability of operation of the switch.

The switch is preferably enclosed within a molded Bakelite casingconsisting of a body member 35 which has the frusto-conical portion 36tting over the shoulder 8, and has the enlarged extending portion 3'!projecting beyond |the spun over end of the shell. A suitable cap member38 has la rabbeted engagement in the end of the portion 31, and issuitably secured thereto by means of cement or the like asy disclosed indetail in said copending application, Serial No. 148,946, filed June 18,1937.

In order to provide for connection of conductors to the terminals of theswitch I preferably provide a terminal lug 4'D as shown in Figure 3which lies upon and is soldered or otherwise mechanically andelectrically connected to the spun over edge 29 of the shell. This lughas an outwardly extending portion 42 which is bent over to form 'a lip43 suitably tapped to receive the screw 44, The portion 42 isof a length`such that the bent over portion 43 lies substantially adjacent theexternal surface of the case 3'I. The terminal conductors may be securedto the lug 4U by the threaded engagement of th-e screw 44 therein.

The terminal lug for the electrode 20 consists of a body member 45 whichengages about the projecting end of the shank 26, and which is suitablysoldered or otherwise secured thereto. This lug has a bent over end 46suitably tapped to receive the screw 47 whereby a terminal conduotor maybe secured thereto. Thus, a positive electrical connection is extendedfrom both the shell 5 and the electrode 20 to the external surface ofthe switch, and the terminal conductors may be secured thereto in anysuitable manner. This facilitates the shipping of the switches in smallsize cartons, and prevents possible damage to terminal conductors whichmight occur if they were fastened to the switch prior to shipping.

In place of the lugs shown in Figures 2 and 3, I may, if desired,provide radially projecting studs 50 and 52 as shown in Figure 4, whichsupplant the bent over lips 43 and 46. The terminal conductors may besecured to the studs in the manner indicated in Figure 4, conductor 53being wound about the stud as indicated, and then suitably soldered orotherwise electrically connected thereto. Ordinarily, the end of theinsulation 54 on the conductor 53 will be frayed, and to prevent furtherunraveling thereof and to protect the connection, I preferably provide ashort length of tubing 55 which may consist of varnished cambric tubingor the like that ts over the insulation and encloses the connection ofthe conductor 53 with the stud 52 or 50.

Considering now in detail the modication of the invention shown inFigures 6 and 7, it will be noted that I provide the standard metallicenvelope type of switch case, such as indicated at 5, and which maycomprise the switch shown in Figure l. Corresponding reference numeralsare applied to the switch itself for the purpose of identification. Theenvelope 5 with the conductors Bil and 62 connected respectively to theshell 5 and the electrode shank 26 is placed within a suitable moldcavity, and the coating is flowed therearound and vulcanized thereto insuch manner as to provide a complete covering for the envelope 5 and thesealed end thereof, which coating or covering 65 has the extension 65forming a reinforcing boss through which the conductors 60 and 62 areled out and the rubber coating is carried and continued along theconductors as indicated at B'l and 68. This, in effect, provides atotally vulcanized covering over the entire switch and the conductorwhich seals the switch itself, and also provides a protective coatingover the conductors so that the switch and portions of the conductorsmay be subjected to corrosive atmospheres, acid or alkali solutions, hotoils and the like without any detrimental action.

I prefer to use a rubber of the Neoprene type impervious to the actionof acidic or basic solutions, and oils of the type used for transformersor for bearing lubrication and the like. This rubber coating may beapplied to the switch case by flowing the same about the switch casewithin a molded cavity and then heating the same under pressure tovulcanize it securely about the case and conductor leads.

In the form of the invention shown in Figures 8 to 11 I rst provide adouble ended switch structure of the type shown in Figure 10 in whichtwo switch cases 'lll and 'l2 are soldered or otherwise mechanicallysecured together, and electrically bonded at their small ends asindicated 3 at 73. The conductor 'I4 forms a terminal lead to the switchcase 15, and consequently through the connection 13 to the switch case12.

The shank 15 of the electrode carried within the ceramic spacer le ofthe switch 10 has a suitable conductor 'Il connected thereto whereby onecircuit is controlled by the mercury making and breaking contact withinthe switch case 10 and closing the circuit between the conductors 14 andTI.

The shank 'I3 of the electrode carried by the switch case 'I2 has aconductor 'i9 connected thereto. The movement of the mercury in theswitch case 'l2 controls the circuit between the conductors 14 and 19.

It will be apparent that when the unit asa whole is rotated or tilted ina clockwise direction, the circuit in switch case 'Ill will be openedand the circuit in switch case 'I2 will be closed, thereby closing thecircuit between the conductors 14 and l. When rotated in the oppositedirection, this circuit is opened and the circuit between the conductors'lil and il is closed within the switch case "i0, Therefore, the unit iscapable of making and breaking two independent circuits upon alternateoperations.

In order to protect the structure shown in Figure 10 I preferablyprovide a molded case formed of insulating material such as a phenolcondensation product, which is formed in two halves, one of the sectionsbeing shown in Figure 8 and indicated generally by the numeral Sil. Thissection is generally semi-cylindrical in form with enlarged end portions82 and $3 which respectively engage over the enlarged ends of the switchcases l'il and T2. The one defining lateral edge of the member 8i! isprovided with a tongue formation such as indicated at 84 in Figure 9,while the opposite lateral edge is provided with the groove indicated at85. Two such members formed in the same manner are tted together overthe construction shown in Figure 10, and are suitably sealed togetheralong the tongue and groove engaging edges indicated by the line 86 inFigure 11. End cap members 88 and 8d are provided for closing the endsof the switch cases 'lil and 12, and may have rabbeted engagement in theends 82 and 83 of the members 8b. Preferably, suitable notches 90 areformed in the switch caps for leading out the two conductors Tl and I9.One of the members 8i! may also be provided with a notch as indicated at92, whereby the conductors M may be passed through the case Bil andconnected to the shell of one of the switch cases 1i) and l2. In orderto secure the cap members 88 and 89 positively in position, suitablesealing compound of the type described in detail in said copendingapplication, Serial No. 148,946, filed June 18, 1937, is provided, whichpositively secures the cap members to the ceramic spacer 16 and over theelectrode connections.

Referring now in more detail to the structure shown in Figure 12, theswitch herein disclosed is of the type operated by rotation of theswitch about its longitudinal axis.

In the preferred form of the structure I provide a base lili? having thetwo supporting stands |62 and |03 which, at their upper ends. providejournals for mounting th-e switch case m4 for rotation. The switch iddis provided with the body portion forming one chamber i215, and with anenlarged end portion lilii joined thereto by the frusto-conical sectionlill. The member 664 is preferably of drawn metal and provides acupshaped shell which farms one electrode for the switch.

Disposed within fractory insuiator |98,

the switch is a ceramic or rewhich has a tapered portion spaced from thetapered portion itil of the shell by a metallic asbestos gasket itscorrespending to the gasket IS of Figure i. The meri ber |63 is providedwith an axially directed recess l'l which is shouldered as indicated ati i to provide a seat for the electrode H2, which electrode has theiiange portion il spaced from the shoulder |i| by means of a inetailicasbestos gasket H4 of a type similar to that shown at iii in Figure 1.

In order to provide for increased surface contact between the body ofmercury ifi-5 and the electrode H2, I preferably recess the inner` faceof the electrode, as indicated at iii, to thereby provide an increasedarea of surface with which the mercury is in contact.

The electrode H2 is held in position by a refractory compression lilwhich prefern ably is formed of a material having relativeiy good heatconductivity. The compression meinber is held in position by acompression ring I I8 which is forced inwardly against the shoulder onthe compression member to force the electrode H2 and the ceramic Hi8axially inwardly of the shell by beading or spinning over the edge i iiiof the shell |06. This locks the parts in fixed position and providesfor compression of the gaskets |09 and ||3 so as to prevent leakage 0ipressure therepast toward the open end of the shell. A suitableinsulating member i125 is disposed about the shank |22 of the electrodelill to space the shell from the standard i, and to thereby insulate theshell therefrom and from the shank |22.

The shank |22 is journalled in 'the standard |03 and has electricalContact therewith. At its outer end it is preferably provided with anarm |24 having a pin |125 projecting therefrom which is adapted to beengaged by any suitable actuating mechanism or by a thermally responsivemember if the switch is employed with temperature controlling mechanism.Rotation of the arm iii results in rotation of the switch It@ in thejournals it?, and i3?, the switch being evacuated through the end li oi'the shell, which is closed by a threaded plug forms the journal for theswitch envelope in the standard |32.

The inner end of the ceramic is provided with a septum |28 which isprovided with a relatively small opening |2i of a size the meniscusheight oi a body of mercury. Through this opening the bodies of mercury|35) and H5 have contacting engagement when the switch is rotated to aposition such that the opening |29 is below the level oi mercury in thechamber |05 and in the chamber i IEB. Rotation of the switch in suchmanner as to bring the opening |29 above this level will csult inbreaking of contact between the shell itil and electrode |52, theparting of the mercury bodies over the edge of the opening |29 effectingthis breaking o contact. It will be noted that the defining edges of theopening i253 are of a shape such that the making and breaking of contactwill occur at substantially the mid-plane of the opening, and willproduce a relatively sharp action whereby the surface tension of themercury will eifect a snap action opening and closing of the circuit andthus reduce the tendency to arcing in the switch.

I may employ a partial li uid ll over the merin connection :ci that alsaf slightly larger than f cury in a switch of this type, such asdescribed in detail in my copending application, Serial No. 745,842,iiled September 28, 1984, in the nature of an ethanolamine, such astriethanolamine. With such a liquid the rate of movement in opening andclosing the circuit will not have any serious tendency to produceexcessive arcing in the switch, even when the switch is rotated veryslowly under the influence of a thermally sensitive or 'humiditysensitive member.

In the embodiment of the invention shown in Figures 13 to 15, inclusive,I have disclosed a switch comprising a refractory separating member,indicated at |35, which is provided with a central portion of reduceddiameter, having the web |35 partially closing the same and forming thepassageway |31 between opposite ends of the member |55. Preferably, theweb |36 is provided with a defining edge of spade-like section asindicated at |33 providing a sharp point over which the two bodies ofmercury |46 and H52 contact and part in closing and opening of theswitch.

In this form of switch, the member |35 is adapted to receive electrodesin the form of cup members |63 and idd at opposite ends thereof whichare suitably secured to the member |35 and preferably are sealed withrespect thereto by the gaskets |i5 and |555. Suitable electricalconductors Uil and Hi8 are connected to the respective electrodes andfrom the terminals of the switch. The entire switch is preferably coatedwith a cellulose acetate coating, indicated at |42, which entirely sealsthe switch and provides a protective coating thereover which may becolored in any desired manner for distinctive appearance.

In the operation of a switch of the type shown in Figures 13y to 15,rotation of the switch about its longitudinal axis produces closing ofthe switch by moving the web |36 from the position shown in Figure 13 tothe position shown in Figure 15, in which it has been rotated out ofposition between the two bodies of mercury lli and H12, and the twobodies of mercury have consequently run together over the sharp edgedpeak of the defining edge Hi8 of the web. Similarly, when the switch isrotated from the position shown in Figure i5 to that shown in Figure 13,the web ISS forces its way through the body of mercury and parts thesame over the dening edge |33 into the separate bodies |45 and |42, eachof which is in contact with the respective electrodes M3 and Mii. Thesharp edge on the web |35 insures a sharp breaking and making ofContact, and results in a snap action eiiect which prevents excessivearcing within the switch chamber. Preferably, the switch chamber isevacuated vthrough one of the electrodes, and the opening is thensecurely sealed by means of the plug |50.

The switch may be rotated in any suitable manner, such as by a plunger,having rocking engagement with the switch or by means of a rack meshingwith a serrated surface |49 of the switch, or in any other suitablemanner. In practice, the switch is never completely rotated, butoscillates between the position shown in Figure 13 and in Figure 15.

It is therefore believed that I have provided a switch structure whichmay be suitably sealed to withstand the high temperature required invulcanizing a rubber covering thereover. Also this construction iscapable of use to provide a double ended switch which may be enclosedwithin a suitable molded case for protection against atmosphere, ormight be enclosed in a rubber covered case for protection againstchemical solutions or hot oils in which the switch might be immersed.

While I am aware that many changes in details of construction might bemade in the illustrated embodiments of the invention, I do not intend tobe limited, except as defined by the scope and spirit of the appendedclaims.

I claim:

1. Gasket means for use in a mercury switch structure of the type havinga cup-shaped rnetallic shell with a frusto-conical shoulder separatingportions of different diameters, a ceramic insert in the enlargedportion of the shell having an external frusto-conical shoulder, anaxial bore in the insert having a cylindrical shouldered recess at theouter end thereof, rand an electrode of disc shape seated in theshouldered recess, comprising metal enclosed asbestos gasket ringsbetween the electrode and the shoulder on the recess and between theshell shoulder and said frusto-conical insert shoulder.

2. In a mercury switch, a cup-shaped metallic envelope, a ceramic insertsealed in the open end of said envelope, an electrode centered in saidinsert and having a projecting shank, said envelope having an arcuatelug member secured radially to the end thereof and having an extendingend` directed axially of the envelope and radially spaced therefrom, asecond lug secured to said shank and having a corresponding directedend, and an enclosing molded case for said switch having notches thereinin which said lug ends are disposed.

3. In a metal envelope type mercury switch, said envelope having aradially inwardly directed end flange, a terminal lug comprising aplanar curved body portion engaging said flange and having a radiallyoutwardly directed end terminating in a normally extending aperturedlip, and a molded insulating case covering said envelope and having anopening in which said lip is adapted to be located.

4. A switch structure comprising two metallic cup shaped shells disposedin axial alinement with their closed ends joined together, a ceramicinsert sealed in the open end of each shell and centering an electrodetherein, bodies of mercury movable in said shells and additional bodiesof mercury retained by said inserts in contact with said electrodeswhereby tilting of said switch results in closing the circuit in oneswitch and simultaneously opening the circuit in the other switch, andan insulating case including two similar semi-cylindrical membersenclosing the annular surface of said structure and end cap piecessecured to the adjacent ends of said members, each of said end cappieces having notches for leading out conductors, one end of one of saidsemi-cylindrical members also having a correspending notch.

5. A closure for a double switch structure of the type comprising twoindividually complete metal envelope mercury switches having enlargedend portions and cylindrical closed body portions, means securing saidbody portions together with the end portions extending in oppositedirections, comprise a multiple piece insulating case formed of twosemi-cylindrical body members and two end cap members entirely closingthe lateral and end surfaces of said structure, said semi-cylindricalbody members having enlarged end portions corresponding to the enlarged7 end portions of said switches.

- ating with the envelope 6. The combination, with a double switchstructure comprising two individually complete metal envelope mercuryswitches having enlarged end portions and cylindrical closed bodyportions, and means securing said body portions together with the endportions extending in opposite directions, of an insulating caseentirely closing the lateral and end surfaces of said structure, saidcasing comprising two body members having semi-cylindrical centralportions with enlarged arcuate ends for enclosing the lateral surface ofthe structure, and two disc-like cap members secured in cylindersdefined by the enlarged ends of said members for completing theenclosure.

7. In a metal envelope type mercury switch having an electrode thereinradially insulated from the envelope and provided with an axiallyprojecting shank, a terminal lug having an apertured end fitting oversaid shank and projecting radially therefrom in axially spaced relationto said envelope, the opposite end of said lug terminating in a normallyextending apertured lip, and a molded case enclosing said envelope andshank and having an opening registering with said lip.

8. A mercury switch comprising a cup-shaped metal shell having anenlarged open end, a ceramic insert in said end having a cylindricalrecess, a radial flange on said insert extending across the inner end ofsaid recess and having an olf-center opening therein, an electrodecentered in and closing the outer end of said recess and radiallyinsulated from said shell by said insert, said electrode being disposedentirely within the outer end of said insert and having a projectingshank, an insulating member laterally enclosing said shank andtelescoping into the outer end of said insert, and mercury bodies incontact with said shell and with said electrode and adapted to contactthrough said opening upon predetermined rotation of said switch.

9. A mercury switch comprising a cup-shaped metallic envelope having anenlarged open end, an insulating insert having a shoulder cooperment ofsaid insert into said envelope, a soft metallic enclosed asbestos gasketmeans between said shoulder and envelope, said insert having an axialbore terminating at its outer end in a radially extending recessedshoulder, an electrode having a disc portion closing said bore and aradial flange, corresponding gasket means between said bore shoulder andsaid flange, an insulating rigid compression member engaging the outerface of said electrode, and means at the open end of said envelope foraxially compressing said flange and insert against said gasket means.

10. The switch of claim 9 further characterized in that said compressionmember telescopes partially into the shouldered portion of the bore toenclose the disc and flange portions in the insert.

11. In a mercury switch comprising a metallic cup-shaped envelope havingan intermediate shoulder and an enlarged open end, an insulating insertin said end and seated against said shoulder, said insert having anaxial bore terminating at the outer end in a radial wall and an enlargedend bore portion, an electrode having a contact portion seated in saidbore and having a radial ange seated in said end bore portion and ofless axial extent, and an insulating compression member partiallytelescoping into said end bore portion against the radial outer face ofsaid flange.

12. The combination of claim 11 further char- 6 acterized in that saidcompression member has a reduced cylindrical portion extending axiallybeyond the open `end of said envelope, and means engaging between theshoulder on said compression member and the spun-over envelope end forholding said assembled parts under pressure.

13. The combination of claim 11 further characterized in that the innerend of said bore is terminated by `an integral radial flange having anoil-center aperture therein providing cornmunication between said boreand the interior of said envelope.

14. In combination, a mercury switch comprising a cup-shaped metalenvelope having an enlarged open end, a ceramic insert in said endhaving a cylindrical chamber therein dened at the outer end by a radialshoulder and an annular axially extending flange, a metal electrode discclosing said end of said chamber and centered Within said ange, gasketmeans between said shoulder and said disc, insulating compression meanscentered in said flange against the outer face of said electrode. saidinsert having a radial ange extending across the opposite end of saidchamber and provided with an off-center aperture, and bodies of mercuryin said envelope and chamber adapted to make and break contact throughsaid aperture upon rotation of said switch.

15. The combination of claim 14 wherein said disc has an axiallyrecessed extension telescoping into said chamber and contacted in allrotated positions of said switch by the mercury in said chamber.

' PAUL S. BEAR.

